1. Field of the Invention
This invention relates to a method and apparatus for improving the determination of proper insertion of a needle.
2. Description of the Related Art
An over-the-needle catheter is a surgical device for insertion into the tissues of a body cavity. A needle and a concentric outer catheter are inserted into the vein of a patient. After insertion, the needle is withdrawn through the emplaced catheter. Fluids can be introduced or removed through the catheter. The problem of quickly determining proper insertion of the needle catheter has persisted in the medical community.
A typical over-the-needle catheter assembly is described in U.S. Pat. No. 4,747,831. In this assembly, a cannula insertion needle projects from the "forward" end of a hollow handle. After the cannula insertion needle is inserted into the patient, the needle is retracted into the handle. A hollow needle is used so that fluids may pass through the needle temporarily while the needle is within the patient. It is disclosed that the needle has a sharpened tip and is made of stainless steel.
One conventional solution for determining when the point of the needle is properly in a blood vessel is to use a transparent housing and flash chamber. U.S. Pat. No. 5,000,740 describes conventional use of a catheter assembly by inserting the concentric catheter and needle through the skin of a patient and into a blood vessel. When the point of the needle is properly located in the vessel, a small amount of blood will flow through the needle and into a flash chamber. Since the needle housing and flash chamber are made of a transparent or translucent polymeric materials, the flow of blood is apparent in the flash chamber. After insertion, the needle is retracted from the catheter into the housing.
Prior art catheters have the disadvantage that after insertion of the catheter into the patient the person inserting the catheter must wait until blood flows into the flash chamber to determine whether or not the catheter has been property inserted. However, the flash chamber is at the end of the catheter that is opposite to the end inserted into the patient. Accordingly, the person inserting the catheter must take his eyes away from the insertion site to check for the appearance of blood in the flash chamber. Prior art catheter also have the disadvantage that if the blood pressure of the patient is low, for example, if the patient is an infant or is suffering from a vascular shutdown, blood may not flow into the flash chamber. Without observing blood in the flash chamber, the person inserting the catheter is unable to determine if the catheter has been properly inserted.
Of possible general relevance to the invention are U.S. Pat. Nos.: 4,850,961; 4,964,854; and 5,053,014 which describe assemblies for over-the-needle catheters.
A practical solution to the problem of expeditiously determining proper insertion of an over the needle catheter in a patient is not found in the prior art.